The purpose of the present research is to increase our understanding of the basic processes of learning and memory, and, in particular, to analyze the changes in those processes that occur during the normal course of development. The general goals of the research are to study the development of habituation and sensitization, long-term memory, stimulus generalization, and reinstatement in the developing rat. Specific projects will focus on the changes with age that occur in (1) the heart rate orienting response, (2) the acquisition, extinction and retention of the conditioned heart rate response, (3) the role of stimulus salience in conditioning, (4) stimulus generalization of conditioned heart rate, (5) potentiation, overshadowing, blocking and lateral inhibition, (6) retroactive and proactive interference, (7) incubation of reinstatement treatments.